spi-gpio: Use PTR_ERR_OR_ZERO() in spi_gpio_request()

Simplify this function implementation by using a known function.

Generated by: scripts/coccinelle/api/ptr_ret.cocci

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/b2dd074a-1693-3aea-42b4-da1f5ec155c4@web.de


Signed-off-by: Mark Brown <broonie@kernel.org>